Obsessional disorder of childhood is a rare disorder which is severely disabling, and about which little is known. The purpose of this protocol is to collect basic data on family history of mental illness, sleep measures, CAT Scans and neuropsychological testing on a selected group of children and adolescents with severe primary obsessional disorder. A drug trial of chlorimipramine or placebo is being carried out to evaluate the effect of the antidepressant and the specificity of chlorimipramine for this disorder.